It has taken me a long time to get my head around the idea of a junction at Agincourt South(west) to connect an Alto line on the CPKC alignment to the MX Stouffville Sub.
My gut reaction all along has been, it's just too tight.... and the differences in elevation seemed vexing.
Anyways, in the end I kind of convinced myself that it is doable..... if......
The elevation of the CP line over the MX line means that Alto has to find a place to cross the CPKC line before then crossing the MX line. Otherwise, it is not possible to tie into the west track of the MX line without flat crossovers that would cause conflicts in routings. So, that means (1) a flyover east of the junction.
The most logical place for that flyover/under is east of Brimley where there are longer distances to address the necessary gradients. I can't see Scarberians wanting a flyover across the backyards of a residential area, and a flyunder would conflict with underpasses at Sheppard and Midland.
Then, going westward, Alto can situate on the south side of CPKC, curving around at the same elevation as the CPKC, with (2) one track crossing over MX before ramping down on the west side, and (3) the other ramping down to MX level on the east side.
That implies the need for two single track ramps from that point down to roughly the 401, with turnouts immediately north of the 401 overpass (otherwise, new tunnels would be needed to widen the 401 underpass). The west side is limited by large new condo towers, but the east side might offer enough room - again with (affordable) expropriation possibly needed. The gradient would be steep but potentially acceptable, depending on how tight the curve is - the gentler the curve, the less linear room for the ramp between the curve and the 401.
The question that arises is - How tight are those curves? I drew curves using a radius of 950 feet, which at 3 inch superelevation is good for 30 mph. Clearly, that encroaches on existing buildings, but the cost of expropriating those is probably reasonable in the overall Alto price tag. Maybe others can survey it a bit differently, but I would just point out that this is a pretty restrictive speed point, beyond the zone where one can say that the train has stopped at Kennedy and is not at track speed yet so no time lost (3.2 miles from the platform at Kennedy) (PS - consider flange squeal on a tight curve on an elevated ramp in the middle of a residential area - it will happen #PearsonUP)
The relative "bills of material" would be
MX routing -
Brimley flyover
New grading south side Brimley to Junction (about 1 km of double track on the south side)
Curved bridge over West Highland Creek
Ramp to east track turnout
Overpass and ramp to west track turnout
Flyover/under at Scarborough Jct (let's be realistic and include this)
Leaside routing -
Brimley flyover (could be anywhere towards Leaside, but let's keep this the same - apples to apples)
New grading south side Brimley to Junction (ditto - about 1 km of double track on the south side)
New 2-track overpass at MX overpass
New grading and track Junction to Leaside (about 7.3 miles, double track)
New bridges at Kennedy (1 track), Ellesmere (2 track) Warden (1 track) Lawrence (2 tracks) Don Mills (2 tracks) Eglinton (2 tracks)
Grade separation at Wicksteed (4 tracks)
Taylor Massey Creek bridge (2 tracks)(300 feet)
East Don River bridge (2 tracks, 900 feet)
West Don River/DVP bridge/embankment (2 tracks, 2000 feet, of which 900 feet is a single bridge)
Refurbish Don Branch, potentially adding double track segments
So yeah, I can concede that the MX routing is definitely cheaper.... but oh, that curvature! And dealing with MX as well. I would trust CPKC more, and stay away from provincial-federal interfaces. And leave LSE with more capacity. Just don't send me the bill ;-)
- Paul
